<?php

    /**
     * PHPExcel_Calculation_Token_Stack
     * Copyright (c) 2006 - 2015 PHPExcel
     * This library is free software; you can redistribute it and/or
     * modify it under the terms of the GNU Lesser General Public
     * License as published by the Free Software Foundation; either
     * version 2.1 of the License, or (at your option) any later version.
     * This library is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     * Lesser General Public License for more details.
     * You should have received a copy of the GNU Lesser General Public
     * License along with this library; if not, write to the Free Software
     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
     * @category   PHPExcel
     * @package    PHPExcel_Calculation
     * @copyright  Copyright (c) 2006 - 2015 PHPExcel (http://www.codeplex.com/PHPExcel)
     * @license    http://www.gnu.org/licenses/old-licenses/lgpl-2.1.txt    LGPL
     * @version    ##VERSION##, ##DATE##
     */
    class PHPExcel_Calculation_Token_Stack {
        /**
         *  The parser stack for formulae
         * @var mixed[]
         */
        private $stack = [];
        /**
         *  Count of entries in the parser stack
         * @var integer
         */
        private $count = 0;

        /**
         * Return the number of entries on the stack
         * @return  integer
         */
        public function count() {
            return $this->count;
        }

        /**
         * Push a new entry onto the stack
         * @param  mixed $type
         * @param  mixed $value
         * @param  mixed $reference
         */
        public function push($type, $value, $reference = null) {
            $this->stack[$this->count++] = [
                'type'      => $type,
                'value'     => $value,
                'reference' => $reference
            ];
            if ($type == 'Function') {
                $localeFunction = PHPExcel_Calculation::localeFunc($value);
                if ($localeFunction != $value) {
                    $this->stack[($this->count - 1)]['localeValue'] = $localeFunction;
                }
            }
        }

        /**
         * Pop the last entry from the stack
         * @return  mixed
         */
        public function pop() {
            if ($this->count > 0) {
                return $this->stack[--$this->count];
            }
            return null;
        }

        /**
         * Return an entry from the stack without removing it
         * @param   integer $n number indicating how far back in the stack we want to look
         * @return  mixed
         */
        public function last($n = 1) {
            if ($this->count - $n < 0) {
                return null;
            }
            return $this->stack[$this->count - $n];
        }

        /**
         * Clear the stack
         */
        public function clear() {
            $this->stack = [];
            $this->count = 0;
        }
    }
